This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-352114, filed Nov. 16, 2001: the entire contents of the application are incorporated herein by reference.
1. Description of the Invention The present invention relates to a blur detection apparatus, particularly to a blur detection apparatus for detecting blur from an unsteady hold on the camera during photographing.
2. Description of the Related Art
In general, when a camera is held in the hands to take a photograph, the camera may be shaken during the exposure particularly where low shutter speeds are required. This is responsible for so-called blur which appears in unsuccessful photographs.
To prevent blurring, various vibration prevention techniques have been proposed. The vibration prevention techniques consist of two parts: a part for detecting vibrations and a part for dealing with the detected vibrations. The latter further comprises a warning technique for informing the user of vibrating conditions and a technique for preventing or correcting deterioration in images due to blurring.
Japanese Patent Publication No. 2001-33870 discloses a technique for warning of blurring wherein a blur warning is displayed on a display element in the finder or on a body that display element is originally meant for displaying photography and date information.
Japanese Patent Publication No. SHO55-106444 discloses a technique for detecting blurring that uses an optical sensor, not a mechanical sensor.
Japanese Patent Publication No. 2001-165622 discloses a technique for detecting blurring using an optical sensor wherein the detection area of the sensor is changed according to the distance to a subject.
However, erroneous detections are often observed.
The blur detection apparatus according to the present invention performs detection of blur on each of plural areas of a light receiving surface of a light receiving element when it detects the blur from a subject image""s positional shifts with time. This allows distinguishing of positional shift of the main subject from that of miscellaneous subjects in the image, realizing precise blur detection.
Preferably, an AF (auto focus) sensor (as an optical sensor) of a camera is used for detecting subject images. This eliminates the need of dedicated detection apparatus, advantageously reducing cost. If the camera is a digital camera, an image pick-up element can also be used.
In preferred applications, only the image position shift in the center part of the light receiving element is used for evaluating blur because the main subjects usually locates in the center of the frame. In this case, image position shifts in the other areas can be used to distinguish blur from other image position shifts such as compositional arrangement change. Of course, more complex logic may also be adaptable. For example, the result of AF ranging data may be used to evaluate the blur since the main subject often locates near to the camera.
Preferably, areas used for evaluating blur are changed depending on the photographic mode or focal length.
The use of image signals for detecting camera movements as described above is not suitable for subjects with insufficient brightness or contrast. A mechanical sensor is preferably integrated and an appropriate blur detection process is selected depending on the subject""s brightness or contrast.
A mechanical sensor and a sensor working on image signals react differently to movements of the camera. Thus, a mechanical sensor that detects in one direction and a sensor working on image signals that detects in another direction are preferably combined.
When a mechanical acceleration sensor is used, the elapsed time between the detection of acceleration in one direction and acceleration in the opposite direction enables the estimate of the magnitude of blurring.
The camera according to the present invention is defined as an apparatus with an image pick-up function and undoubtedly includes dedicated apparatus such as film camera, digital cameras, and video cameras. In addition, PDAs, personal computers, and cellular phones, which are provided with an image pick-up function, and their image pick-up units are also included.